Bad Internet Explorer..........................

I have been running XP proffessional for a while now with no grief until my Internet Explorer stopped running multiple windows. I can open Internet explorer but cant open more than one window without "error message" and a forced shutdown of the window. Im using Mozilla now and thats working fine, but life in Microsofts world cannot be without I.E. !!! Please help//////

Thanks for the quick responses guys....
I tried the upgrades and the system retore unsuccesfully. I just attemted to scan the system using the repair method as advised by xsivforce and was promted for the windows xp cd. I think thats a good sign cause it seems like theres a dll file to be repaired but I dont have my cd handy. Ill let ya know what happens later. Again, thanks both of you.